1. Field of the Invention
The present invention relates to a blade for electrophotographic apparatus which blade is used in electrophotographic apparatus, and a process for manufacturing the same.
2. Description of the Related Art
In general, in electrophotographic apparatus, images are formed in such a cycle that a toner in a developer container is uniformly charged, which is then made to adhere to an electrostatic latent image on a photosensitive member to develop the latent image to form a toner image, thereafter the toner image is transferred to a recording medium such as a paper sheet, a belt, and thereafter any toner remaining on the photosensitive member is removed. Accordingly, the electrophotographic apparatus are each provided with, e.g., a cleaning blade which is made up of a support and joined thereto a blade member, and a developer blade which forms a thin layer of toner while triboelectrically charging the toner in the developer container.
This cleaning blade is required to have various properties and performance. They may include, e.g., wear resistance for making the blade highly durable, low frictional properties for preventing its turn-over, noise generation and making the photosensitive member drivable at a low torque, cleaning performance in broader environmental ranges, and resistance to compression set caused by its long-term pressure touch with the photosensitive member. In recent years, with much further progress toward high-speed printing and high durability and also for the purpose of making image quality higher, toners have been made to have spherical particles and small particle diameter, and hence the cleaning blade is sought to have the above properties and performance at higher levels.
Conventionally, the cleaning blade is integrally formed of a support member made of a metal, through which the blade is to be attached to an electrophotographic apparatus or the like, and a blade member made of an elastic material, which stands attached to one end portion of the support member. Then, as a material for making up the blade member, a heat-curable polyurethane elastomer is usually used as being excellent in the wear resistance and the resistance to compression set.
Here, in order for the cleaning blade to be improved in cleaning performance, it is considered to bring the cleaning blade into touch with the photosensitive member at a higher pressure, i.e., to make larger the level of penetration in bringing the blade into touch with the photosensitive member. In such a case, however, a large frictional force may come between the cleaning blade and the photosensitive member to remarkably cause problems that the cleaning blade turns over, makes noise and makes the photosensitive member driven at a high torque. Hence, it is sought to make the cleaning blade low frictional at its part coming into touch with the photosensitive member.
Accordingly, in order to make the blade low frictional at its part coming into touch with any member (hereinafter this part is also termed “touching part”), various methods have conventionally been attempted.    (1) As a first method, a method may be given in which a blade is coated on its surface with a lubricating powder.    (2) As a second method, a method may be given in which a blade material heat-curable polyurethane elastomer is made highly hard as a whole to make the blade low frictional.    (3) As a third method, a method may be given in which a blade member made of a heat-curable polyurethane elastomer is made low frictional only at its surface to keep elasticity of the whole blade. For example, as disclosed in Japanese Patent Application Laid-open No. 2007-163676, a liquid synthetic resin that forms a partial layer is casted in the form of a bead into one mold of a split mold, and thereafter the mold is assembled and then a base layer is formed so as to make the blade member highly hard and highly repulsive only at its touching part to make it low frictional at that part. The method disclosed in Japanese Patent Application Laid-open No. 2007-163676 enables manufacture of a blade for electrophotographic apparatus in which, as shown in FIG. 1, touching part 3 coming into touch with a photosensitive member or the like is formed of a material different from that for a blade member 2 attached to one end portion of a support member 1.
The above methods, however, have brought about problems as stated below.    (1) In the first method, it may be difficult to perform uniform coating. Also, the coating formed may tend to come off to result in a poor durability. Further, it follows to use a halogen type organic solvent when coated, which may be undesirable for environment.    (2) In the second method, if the blade material is made highly hard to a level of making it low frictional, it may scratch the photosensitive member or developing roller. Also, the blade may come insufficient in rubber elasticity required therefor.    (3) In the third method, a touching part made of a different material is partially formed on the blade member at its touching face, and hence the touching part may come separated from the blade member where the level of penetration in bringing the blade into touch with the photosensitive member is set larger or where the blade is made highly durable.